Device for conical tapering of tubes of circular cross section

ABSTRACT

A device for conical tapering of a continuously rotating tube about the longitudinal axis thereof and having a circular cross section. The tube is simultaneously advanced in the axial direction and has two tools which are fed in radially of the tube and are arranged in one plane perpendicular to the tube axis. At least one of the tools consists of two working surfaces which are fixedly connected and define an angle with the infeed direction of the tool. The device also consists of a mandrel. The mandrel has a guide which is adjustable with the tools relative to the tube in the axial direction and guides the mandrel axially with respect to the tools and is held by a spring force which acts in the direction of the tube advance as seen from the mandrel. The mandrel is positioned with its tapered end between the tools.

United States Patent [191 Thamasett I 1 DEVICE FOR CONICAL TAPERING OF TUBES OF CIRCULAR CROSS SECTION [75] Inventor: Eberhard Thamasett, Reutti,

Germany [73] Assignee'. Wieland-Werke AG, Ulm, Germany [22] Filed: Apr. 6, 1973 [21 Appl. No.: 348,760

1301 Foreign Application Priority Data Apr. 12, 1972 Germany 2217505 [52I US. Cl. 72/96, 72/283 [51] Int. Cl B2ld 51/10 5 Field of Search 72/76, 96, 276, 283, 209

[56] 2 References Cited UNITED STATES PATENTS 1,819,376 8/1931 Muller 72/76 2,224.838 12/1940 Smith 72/283 FOREIGN PATENTS OR APPLICATIONS 1.285.433 12/1968 Germany 72/76 Primary Examiner-Lowell A. Larson Attorney, Agent, or FirmWoodhams,Blanchard and Flynn [57] ABSTRACT A device for conical tapering of a continuously rotating tube about the longitudinal axis thereof and having a circular cross section. The tube is simultaneously advanced in the axial direction and has two tools which are fed in radially of the tube and are arranged in one plane perpendicular to the tube axis. At least one of the tools consists of two working surfaces which are fixedly connected and define an angle with the infeed direction of the tool. The device also consists of a mandrel. The mandrel has a guide which is adjustable with the tools relative to the tube in the axial direction and guides the mandrel axially with respect to the tools and is held by a spring force which acts in the direction of the tube advance as seen from the mandrel. The mandrel is positioned with its tapered end between the tools.

8 Claims, 3 Drawing Figures PATENTED HOV 12 I974 SHEET 2 OF 2 DEVICE FOR CONICAL TAPERING OF TUBES OF CIRCULAR CROSS SECTION FIELD OF THE INVENTION The invention relates to a device for the conical tapering of a rotating tube rotatable about the longitudinal axis thereof and having a circular cross section. The tube is also simultaneously advanced in the axial direction. The device comprises two tools which are fed in radially of the tube and are arranged in one plane perpendicularly to the tube axis, of which tools at least one consists of two working surfaces which are fixedly connected (nonshiftable relative to each other) and which define an angle with the infeed direction of the tool and a mandrel.

BACKGROUND OF THE INVENTION Devices of this type are, for example, known from German Auslegeschrift No. 1,285,433. Particularly in the case of tubes having a thin tube wall thickness, it is necessary in connection with such a known device to provide a mandrel which supports the tube wall during the processing by the tools and which can be adjusted from outside against the tube. The tube is thereby tensioned above the mandrel and is rotated therewith. The tools which are adjusted against the tube from outside cause the wall of the tube to rest against the mandrel, whereby at least also the wall thickness is slightly reduced in thickness. In the end, the mandrel rests relative to the tube and the shape of the mandrel corresponds exactly to the desired inside shape of the tube. If a reduction of the tube diameter is to take place during several passages of the tools, then just as many mandrels having the corresponding intermediate shapes are required.

The manufacture of such mandrels, particularly in the case of long tubes having smalldiameters, is very expensive. Often the tool expense is so high that the manufacture of conical tapered tubes in small numbers is not economical. The expense is considerable particularly in the case of double-conical tubes, as for example Venturi tubes, because the long mandrels must be constructed in two parts. Tubes, the diameter of which is reduced and enlarged lengthwise of the tube axis, cannot at all be conically tapered with the known device.

The basic purpose of the invention is to provide a device of the type mentioned above but wherein a plurality of mandrels is no longer required and the mandrel shape can in its entirety be substantially simplified and be independent of the respective desired final shape of the tube.

This purpose is attained according to the invention in such a manner that the mandrel has a guide which is adjustable together with the tools relative to the tube in the axial direction, in which guide it is axially movable with respect to the tools and is held by a spring force which acts in the direction of the tube advance as seen from the mandrel, whereby the mandrel lies with its end, which in this direction is the front end and which is tapered approximately conically, between the tools.

Contrary to the known device, in which the mandrel extends over the entire length-of the tube which is to be conically tapered and corresponds to the desired final shape of this tube, according to the invention the operation is carried out by utilizing a relatively short mandrel which is not moved with the tube but with the tools, over which mandrel the tube is pulled from behind. The shape of the mandrel thereby does not correspond to the inside shape of the tube but is adjusted approximately to the shape of the working surfaces in the drawing-in zone of the tools so that the mandrel with its tapered end part supports the wall of the tube almost over its entire zone in which the deformation of the tube takes place and during the entire longitudinal adjustment of tools and tube. The resilient mounting of the mandrel effects thereby a continuous pressing of the tapered mandrel part against the tube wall and permits moreover the mandrel to move backward with a progressing infeed of the tools to the smallest tube diameter against the spring force so that the infeed of the tools is not hindered by the mandrel. Therefore, in the case of a large tube diameter, the mandrel is moved with its conically tapered end part only deeper between the tools than in the case of a small tube diameter.

In a preferred embodiment, the mandrel is held on a mandrel rod and supports at least the length of the tube to be conically tapered, which mandrel rod is guided in the zone of its endremote from the mandrel axially mov'ably on a machine table. which also carries the tools. Both the tools and also the mandrel rod having the mandrel held thereon can be adjusted together longitudinally of the tube which is to be conically tapered by means of the machine table. Advantageously the mandrel rod is to be only slightly smaller in diameter than the original inside diameter of the tube to be conically tapered. The mandrel rod can therefore securely guide the tube while rotating at a high rotational speed during the machining operation. In order to assure in a simple manner that the tube, which is to be conically tapered is moved prior to the start of the machining process always evenly far over the mandrel and the mandrel rod," it is advisable to provide the mandrel rod with a stop ring for the tube so that the stop ring can be adjusted lengthwise of the mandrel rod.

To produce the spring force which folds the mandrel, the mandrel rod is, according to a further suggestion of the invention, under the effect of a pressure spring which is arranged between a guide part of the machine table, which guide part carries the mandrel rod, and a setting ring guided on the mandrel rod. The mandrel rod has advantageously a stop which limits its advance in direction of the tools, which stop fixes the front final position of the mandrel and overcomes the danger that the tools at the beginning of the conical-taperin g operation are fed in on the cylindrical part of the mandrel. It is within the scope of the invention to support the mandrel rotatably about its axis. The mandrelcan then take part in the rotation of the tube which must be conically tapered, and because the force application zones of the tools move over the mandrel periphery corresponding with the rotation, the mandrel is worn completely evenly by the tube and therefore prolongs the life of the mandrel.

The cone angle of the mandrel can be changed over a wide range. Toward small values the cone angle is limited in such a manner that the tapered mandrel part may not get so slender that it, under the pressure of the outer tools which are adjusted against the tube, hecomes self-locking within the tube and therefore during a further infeed of the tools cannot move back against the spring force. Toward large cone angles, a limitation is obtained in such a manner that the reduction of the tube diameter should not take place steplike but slowly over a sufficiently large longitudinal zone of the tube which is to be conically tapered, whereby said longitudinal zone corresponds approximately to the drawingin zone of the tools which are to be adjusted from outside against the tube. If in the case of a large cone angle, the mandrel with its tapered part becomes substantially shorter with respect to this drawing-in zone, and it then carries the tube wall during the conical-tapering operation practically only in an extremely narrow, almost line-shaped zone between the conical and the following cylindrical mandrel part. In any case, it is desirable to round off the mandrel in the axial direction in the transition zone from the cylindrical part of the mandrel to the approximately conically tapered mandrel part in order to achieve a zone which is as large as possible, in which zone the mandrel rests against the tube wall, and therewith also a correspondingly little wear of the mandrel. Moreover, the cone angle of the mandrel depends also on whether simultaneously with the conical tapering of the tube a reduction in the thickness of the tube wall is desired. Smaller cone angles result in stronger reductions in wall thickness, increasing cone angles result in stronger thickenings of the tube wall. In the end, the advantages achieved with the invention consist substantially in that instead of a plurality of long mandrels for various cone shapes and lengths, like also for various intermediate dimensions of the tubes, in the case of the invention only a short mandrel is required which to a great degree lowers the manufacturing expense of conically tapered tubes and the expense with respect to storage of the mandrels. The shape of the conically tapered tubes depends only from the infeed of the outer tools, that is for example when a copying device is used only from the shape of the template. The wall thickness of the conically tapered tube can in the conical tube zone be well influenced by the spring force supporting the mandrel and the cone angle of the mandrel. Thus it is possible to manufacture with the device of the invention tube shapes with diameters which decrease and increase successively as often as desired, which tube shapes could not be manufactured with the known devices or only by putting together several conical individual pieces. During the manufacture of short conical tubes, this advantage can be used by conically tapering such tubes in multiple length and by dividing same thereafter. A further advantage of the invention I consists of the tube diameter being reduced to a substantially greater degree during one passage of the tools and of the tube wall being supported almost over the entire range of effectiveness by the conical part of the mandrel.

BRIEF DESCRIPTION OF TI-IE DRAWINGS The invention will be discussed more in detail in con- I nection with one exemplary embodiment which is illustrated in the drawings, in which:

FIG. 1 is a front view of the device of the invention as viewed in the axial direction of the tube which is to be conically tapered,

FIG. 2 is a longitudinal cross-sectional view of the device along a horizontal plane of the tube axis,

FIG. 3 is a vertical longitudinal cross-sectional view of the device according to FIGS. 1 and 2 along a vertical plane of the tube axis.

, DETAILED DESCRIPTION In the schematically illustrated device in the drawings for conical tapering of long tubes 1, two tools 2 are provided which are of a platelike shape in the exemplary embodiment and move against one another in the direction of the illustrated arrows 13, which arrows indicate the infeed direction of the tools 2.'The tools 2 are, for example, secured to movable carriages 3 supported on rollers 4 which are guided on a machine table 5 which is adapted to move in the longitudinal direction of the tube 1. The tools 2 are fed inwardly toward each ,other during a continuous rotation of the tube I about the longitudinal axis thereof. The tools 2 are also simultaneously fed in the axial direction by a movement of the machine table 5 in a direction corresponding to the arrows 14 in FIGS. 2 and 3. A rotatingly driven chuck 15 is adapted to engage one end of the tube 1 and is used to rotatingly drive the tube 1 in the direction of the arrows 16 in FIGS. 2 and 3. A mandrel 7 is mounted on a mandrel rod 6 and is positioned in the range of effectiveness of the tools 2. The mandrel 7 has a cylindrical mandrel part 7b and a conical mandrel part 7a which is tapered away from the cylindrical part in the direction of the tube advance (arrow 17 in FIG. 3). The mandrel 7 engages and supportsthe inside portion of the wall of the tube 1 in the zone of the working surfaces 18 on the tools 2 by means of its cone-shaped surface 22. The tapered mandrel part 7a corresponds in shape approximately to the shape of the working surfaces 18 in the drawing-in zone of the tools 2. In the drawing-in zone, the working surfaces 18 are inclined relative to the tube axis and are rounded off at the location 19 which forms the most narrow passage for the tube .1. The mandrel rod 6is held at an end remote from the mandrel 7 by a guide part 8 which is fixedly connected to the machine table 5. With the help of the machine table 5, it is therefore possible to adjust both the tools 2 and themandrel 7 relative to the tube 1 in direction of the arrows l4 and vice versa. A coil spring 9 presses the mandrel rod 6 and the mandrel 7 forwardly into the conically shaped recess formed in the tools 2. A forward limit position of the mandrel 7 is fixed by an adjustable stop ring 10. The coil spring 9 permits at the same time a yielding or a rearward retraction of the mandrel 7 during the infeed of the tools 2. The setting ring 11 is adjustable and permits an adjustment of the initial tension of the pressure spring 9. The mandrel rod 6 is only a little smaller in diameter than the inside diameter of the tube 1 so that a good guide for the tube is formed to facilitate a high speed rotational drive of the tube 1 on the mandrel rod 6. The adjustable stop ring 12 is used to bring all tubes into the same initial position prior to the conical tapering oper-.

ation. The mandrel 7 is rounded off in the axial direction in the transition zone between its tapering part 7a and the cylindrical part 7b, as indicated at 20 in FIG. 2

a maximum spring force of 8 kp., had a cone angle of The thickness of the tube wall at A (FIG. 2) was 1.0 mm. When the cone angle of the mandrel was enlarged to 30, the wall of the tube increased in thickness at A to 1.2 mm. At a maximum spring force of 40 kp. and a cone angle of 20, the original wall thickness was reduced at A to 0.6 mm.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a mandrel support device for providing a conical taper on a tube having a circular cross section during a simultaneously occurring continuous rotation of said tube about a longitudinal axis and an axial feed thereof, a pair of tools arranged in one plane perpendicular to said longitudinal axis and which can be fed radially of said longitudinal axis, at least one of said tools being composed of two operating surfaces which are fixedly connected with one another and defining an angle with said longitudinal axis of said tool, means defining a mandrel having guide means which is adjustable together with said tools relative to said tubes in said axial direction and supports said mandrel for movement with respect to said tools, said mandrel having an approximately conically tapered end at its free end located between said tools, the improvement comprising resilient means connected between said guide means and said mandrel for resiliently urging said mandrel toward said operating surfaces, said resilient means providing the only force for urging said mandrel toward said operating surfaces.

2. The improvement according to claim 1, wherein said mandrel is secured to a mandrel rod which has a length equal to at least the length of the tube which must be conically tapered, said mandrel rod being guided in the zone of its end remote from said mandrel and axially movable on a machine table which also carries said tools.

3. The improvement according to claim 2, wherein said resilient means comprises a pressure spring for producing the spring force on said mandrel, said mandrel rod being under the effect of said pressure spring which is arranged between said guide means on the machine table which guide means carries said'mandrel rod and a setting ring which is mounted on said mandrel rod.

4. The improvement according to claim 2, wherein said mandrel rod carries a stop which is adjustable and limits its advance in direction of said tools.

5. The improvement according to claim 2, wherein said mandrel rod is only slightly smaller in diameter than the original inside diameter of the tube which is to be conically tapered.

6. The improvement according to claim 2, wherein said mandrel rod has a stop ring for the tube which must be conically tapered.

7. The improvement according to claim 1, wherein said mandrel is supported rotatably about its axis.

8. The improvement according to claim 1, wherein said mandrel is rounded off in axial direction in the transition from a cylinder to the slightly conically tapered zone. 

1. In a mandrel support device for providing a conical taper on a tube having a circular cross section during a simultaneously occurring continuous rotation of said tube about a longitudinal axis and an axial feed thereof, a pair of tools arranged in one plane perpendicular to said longitudinal axis and which can be fed radially of said longitudinal axis, at least one of said tools being composed of two operating surfaces which are Fixedly connected with one another and defining an angle with said longitudinal axis of said tool, means defining a mandrel having guide means which is adjustable together with said tools relative to said tubes in said axial direction and supports said mandrel for movement with respect to said tools, said mandrel having an approximately conically tapered end at its free end located between said tools, the improvement comprising resilient means connected between said guide means and said mandrel for resiliently urging said mandrel toward said operating surfaces, said resilient means providing the only force for urging said mandrel toward said operating surfaces.
 2. The improvement according to claim 1, wherein said mandrel is secured to a mandrel rod which has a length equal to at least the length of the tube which must be conically tapered, said mandrel rod being guided in the zone of its end remote from said mandrel and axially movable on a machine table which also carries said tools.
 3. The improvement according to claim 2, wherein said resilient means comprises a pressure spring for producing the spring force on said mandrel, said mandrel rod being under the effect of said pressure spring which is arranged between said guide means on the machine table which guide means carries said mandrel rod and a setting ring which is mounted on said mandrel rod.
 4. The improvement according to claim 2, wherein said mandrel rod carries a stop which is adjustable and limits its advance in direction of said tools.
 5. The improvement according to claim 2, wherein said mandrel rod is only slightly smaller in diameter than the original inside diameter of the tube which is to be conically tapered.
 6. The improvement according to claim 2, wherein said mandrel rod has a stop ring for the tube which must be conically tapered.
 7. The improvement according to claim 1, wherein said mandrel is supported rotatably about its axis.
 8. The improvement according to claim 1, wherein said mandrel is rounded off in axial direction in the transition from a cylinder to the slightly conically tapered zone. 